Composition for and method of altering the permeability of a subterranean formation

ABSTRACT

A crosslinking composition and method for reducing the permeability of a subterranean formation. The crosslinking composition comprises aluminum cations having a valence of 3+ and zirconium cations having a valence of 4+.

This application is a division, of application Ser. No. 607,363, filed05/04/84 now U.S. Pat. No. 4,606,772.

BACKGROUND OF THE INVENTION

A. FIELD OF THE INVENTION

This invention relates to a method of treating a subterranean formationof non-uniform permeability, and more particularly concerns a method ofreducing the permeability of subterranean formations to water therebypromoting better control of fluid injection patterns in the secondary ortertiary recovery of hydrocarbons and achieving water reduction inproducing wells and thus reducing the quantity of water recovered from asubterranean formation penetrated by a well bore whereby the relativeproduction rate of the hydrocarbons is increased.

B. DESCRIPTION OF THE PRIOR ART:

Since only a portion of the oil contained in a subterranean reservoircan be recovered by primary methods, it has become general practice toemploy various secondary or tertiary recovery techniques to produce theadditional quantities of oil not economically recovered by primarymethods. Of the various secondary or tertiary recovery methodsavailable, one of the most widely practiced techniques is thedisplacement of oil from the reservoir with a driving fluid such as afloodwater injected for that purpose. Normally, in carrying out theflooding process, input or injection wells are utilized. These wells canbe old existing wells or can be wells which are newly drilled into theoil-producing strata. The injection wells locations with reference tothe production wells are selected to afford a desired flood pattern, theselected pattern depending in part upon field conditions, the locationsof existing wells, and the operator's preference. Aqueous drive fluids,such as water, brine, or a viscous aqueous fluid are forced into theinput wells under pressure, and out into the surrounding oil bearingstrata towards the producing well or wells. While waterflooding has beenrather widely practiced in recent years, it is not without considerableoperating problems and economical limitations particularly thoseassociated with low oil recoveries in proportion to the amount of waterinjected. Various surfactant and solvent floods have been proposed asmeans for recovering additional quantities of oil over that recoverableby conventional waterflooding. However, these processes face seriousoperating problems when practiced in heterogeneous formations containingstrata or channels having permeability substantially higher than thebulk of the formation.

One of the major problems encountered in a flooding operation is thebreakthrough of the flooding medium from the flood front to theproducing well relatively early in the displacement process and rapidlyincreasing producing water/oil ratios following the initialbreakthrough. These difficulties result from the displacing mediumchanneling or fingering through the oil-bearing structure to theproducing well, thus bypassing large zones of the oil-bearing strata.The reason for the channeling of the flooding medium to the producingwells and the resulting low oil recovery is due in part to the peculiarstructure of the oil-bearing strata. Underground oil reservoirs, in mostcases, consist of layers of sand or rock and, since no reservoir rock isperfectly uniform in composition and structure, the permeability willvary across the rock face or strata. Also, fractures, cracks, and otherabnormalities can promote channeling of the displacement of the fluid.

In the normal flooding operation, maximum oil recovery is obtained whenthe driven fluid goes up in a wide bank in front of the driving fluidwhich moves uniformly towards the producing well. To keep this bank ofoil intact and constantly moving towards the producing well, asubstantially uniform permeability must exist throughout the strata. Ifthis uniform permeability does not exist, or is not provided, theflooding fluid will seek the areas of high permeability, and channelingoccurs with the subsequent loss of some driving fluid energy and theappearance of excessive amounts of driving fluid in the producing well.Moreover, as the more permeable strata are depleted, the driving fluidhas a tendency to follow channels and further increase the consumptionof the flooding medium to the point where the process becomesuneconomical. It is, therefore, desirable to operate at a drive fluid tooil ratio that is as low as possible.

Another problem associated with the production of oil from oil-bearingformations containing highly permeable water channels communicating theproduction well with the water zone is the intrusion of water into thewell. Not only does this water intrusion cause production and disposalproblems, but more importantly the beneficial effect of the naturalwater drive is at least, in part, lost thereby adversely affecting oilrecovery.

It is advantageous to reduce the permeability of the water channels soas to render the formation more uniformly permeable and to increase theunit efficiency of the water drive, or alternatively to shut off thewater intrusion.

Many processes have been proposed for reducing the permeability of asubterranean formation. For instance, U.S. Pat. No. 3,762,476 disclosesthat the quantity of water recovered from a subterranean formationpenetrated by a well bore can be reduced by injecting into thesubterranean formation a first thickened aqueous solution, a complexingionic solution of multivalent cations and retarding anions, a brineslug, and a second thickened aqueous solution. Complexing ionicsolutions disclosed in the patent have a multivalent metal cationselected from the group consisting of Fe²⁺, Fe³⁺, Al³⁺, Ti⁴⁺, Zn²⁺,Sn⁴⁺, Ca²⁺, Mg²⁺, and Cr³⁺ and a retarding anion selected from the groupconsisting of acetate, nitrilotriacetate, tartrate, citrate andphosphate.

U.S. Pat. No. 3,833,061 discloses a method for selectively reducing thepermeability of an oil-wet subterranean formation penetrated by at leastone well bore by passing an oxidizing agent through and into contactwith the formation for oxidizing and removing hydrocarbons from thesurfaces of the formation and thereafter contacting the treatedformation surfaces with a crosslinked polymer. The patent discloses theuse of aluminum citrate as a crosslinking composition.

SUMMARY OF THE INVENTION

By the present invention, crosslinking compositions containing aluminumcations having a valence of 3⁺ and zirconium cations having a valence of4⁺ are provided. These crosslinking compositions when mixed with anaqueous fluid containing a polymer having a molecular weight greaterthan 100,000 and containing carboxyl functionality produce a viscosityincrease in the fluid in excess of the individual aluminum and zirconiumcomponents of the crosslinking compositions.

The present invention also provides a method of reducing thepermeability of a subterranean formation penetrated by at least one wellbore by treating the formation surfaces with a crosslinked polymer. Themethod of the invention can be used in either injection wells of waterfloods or hydrocarbon production wells for the purpose of reducing thewater-oil ratio produced therefrom, e.g., reduce the mobility of waterin the well bore area.

In one embodiment of the present invention, the permeability of thesubterranean formation is altered by contacting the formation with anaqueous mixture comprising a water dispersible hydrophilic organicpolymer having a molecular weight greater than 100,000 and containingcarboxyl functionality and a crosslinking composition comprising:

(a) water;

(b) a first ingredient containing aluminum cations having a valence of3⁺ and comprising aluminum acetate;

(c) a second ingredient containing zirconium cations having a valence of4⁺ and selected from the group consisting of:

(i) zirconium lactate;

(ii) a zirconium admixture comprising:

(A) a zirconium compound selected from the group consisting of zirconiumoxychloride, zirconium acetate, zirconium tetrachloride, zirconiumorthosulfate, zirconium carbonate, zirconium ammonium carbonate, andmixtures thereof;

(B) an alpha-hydroxy acid represented by the following formula: ##STR1##wherein: R is selected from the group consisting of hydrogen and analkyl group having 1 to about 3 carbon atoms; and,

(C) an amine compound represented by the formula: ##STR2## wherein: R₁is a hydroxyalkyl group having 1 to about 3 carbon atoms;

R₂ is selected from the group consisting of an alkyl group having 1 toabout 3 carbon atoms and a hydroxyalkyl group having 1 to about 3 carbonatoms;

R₃ is selected from the group consisting of hydrogen, an alkyl grouphaving 1 to about 3 carbon atoms and a hydroxyalkyl group having 1 toabout 3 carbon atoms; and,

(iii) mixtures of (i) and (ii).

The zirconium cations and aluminum cations are present in saidcrosslinking composition in an amount sufficient to produce a weightratio of zirconium cations to aluminum cations of from about to 1 toabout 10 to 1.

In another embodiment of the present invention, the subterraneanformation is contacted sequentially with a first mixture comprisingwater and a water dispersible hydrophilic organic polymer having amolecular weight greater than 100,000 and containing carboxylfunctionality, optionally a spacer fluid, an aqueous crosslinkingcomposition comprising:

(a) water;

(b) a first ingredient containing aluminum cations having a valence of3⁺ and comprising aluminum acetate;

(c) a second ingredient containing zirconium cations having a valence of4⁺ and selected from the group consisting of:

(i) zirconium lactate;

(ii) a zirconium admixture comprising:

(A) a zirconium compound selected from the group consisting of zirconiumoxychloride, zirconium acetate, zirconium tetrachloride, zirconiumorthosulfate, zirconium carbonate, zirconium ammonium carbonate, andmixture thereof;

(B) an alpha-hydroxy acid represented by the following formula: ##STR3##wherein: R is selected from the group consisting of hydrogen and analkyl group having 1 to about 3 carbon atoms;

(C) an amine compound represented by the formula: ##STR4## wherein: R₁is a hydroxyalkyl group having 1 to about 3 carbon atoms;

R₂ is selected from the group consisting of an alkyl group having 1 toabout 3 carbon atoms and a hydroxyalkyl group having 1 to about 3 carbonatoms;

R₃ is selected from the group consisting of hydrogen, an alkyl grouphaving 1 to about 3 carbon atoms and a hydroxyalkyl group having 1 toabout 3 carbon atoms; and,

(iii) mixtures of (i) and (ii);

wherein said zirconium cations and said aluminum cations are present insaid crosslinking composition in an amount sufficient to produce aweight ratio of zirconium cations to aluminum cations of from about 1 to1 to about 10 to 1; optionally a spacer fluid; and finally with a secondmixture comprising water and a hydrophilic organic polymer having amolecular weight greater than 100,000 and containing carboxylfunctionality.

The use of the method of the invention results in a reduction inpermeability of the subterranean formation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polymers suitable for use in the present invention can generally bedescribed as water dispersible hydrophilic organic polymers having amolecular weight greater than 100,000 and containing carboxylfunctionality whereby the polymers can be crosslinked with thecrosslinking composition. Examples of such polymers include carboxyalkylguar wherein the alkyl group has 1 to about 3 carbon atoms,carboxyalkylhydroxyalkyl guar wherein the alkyl groups have 1 to about 3carbon atoms, xanthan gum, polyacrylamide and polymethacrylamide whereinfrom about 5 to about 75 percent of the carboxylamide groups of thepolyacrylamide and polymethacrylamide are hydrolyzed to carboxyl groups,cellulose ether polymers containing carboxyl functionality, andcopolymers resulting from the polymerization of acrylamide ormethacrylamide with acrylic acid and/or methacrylic acid.

The polymers used in the present invention are preferably substantiallyfree of crosslinking between the polymer chains. As used herein and inthe claims, unless otherwise specified, the term "hydrolyzed" includesmodified polymers wherein the carboxyl groups are in the acid form andalso polymers wherein the carboxyl groups are in the salt form, providedsuch salts are water dispersible. Such salts include ammonium salts,alkali metal salts, and others which are water dispersible. Hydrolysiscan be carried out in any suitable fashion, for example, by heating anaqueous solution of the polymer with a suitable amount of sodiumhydroxide.

Examples of cellulose ethers which can be used to carry out theinvention include, for example, carboxyalkyl cellulose ethers such ascarboxymethyl cellulose (CMC), and mixed ethers such ascarboxyalkylhydroxyalkyl cellulose ethers such ascarboxymethylhydroxyethyl cellulose (CMHEC). Many of these celluloseethers that contain carboxyl functionality are commercially availableand are available as the alkali metal salt, usually the sodium salt. Themetal is seldom referred to and they are commonly referred to as CMC orCMHEC.

The copolymers of acrylic acid, methacrylic acid or combinations thereofwith acrylamide, methacrylamide or combinations thereof are made up withfrom about 5 to 70 percent by weight of acrylic acid, methacrylic acidand combinations thereof and most preferably from about 10 to about 40percent by weight of acrylic acid, methacrylic acid and combinationsthereof.

Included among the polyacrylamides that can be used in the presentinvention are polyacrylamides and related polymers which are watersoluble. Presently preferred polymers include homopolymers andcopolymers of acrylamide and methacrylamide. These polymers can containfrom about 5 percent to about 75 percent and preferably about 40 percentof the carboxamide groups hydrolyzed to carboxyl groups.

The most preferred polymer for carrying out the method of the inventionis polyacrylamide wherein 7 percent or 30 percent of the carboxamidegroups are hydrolyzed to carboxyl groups. The amount of carboxylfunctionality will depend on the formation to be treated.

The polymers must have a molecular weight of at least 100,000, but theupper limit of the molecular weight is not critical as long as thepolymer is water dispersible and the aqueous gel prepared therefrom canbe pumped. Thus, polymers having a molecular weight as high as 20million or higher, in many said conditions can be used.

The amount of the polymers used in the practice of the invention canvary widely depending on the particular polymer desired, purity of thepolymer, and the properties desired in the gels. Generally speaking,amounts in the range of from 0.0025 to about 5.0, preferably from 0.01to 1.5, or preferably 0.025 to about 0.4 weight percent based on theweight of water in the aqueous mixture can be used. Amounts outside thisrange, however, can be used. Small amounts of polymer will usuallyproduce liquid mobile gels which can be readily pumped where as largeamounts of polymer will usually produce thick, viscous, somewhat elasticgels. The thick gels can be thinned by the dissolution of water to anydesired concentration of polymer and this can be done by mechanicalmeans such as stirring, pumping, or by means of a suitable turbulenceinducing device to cause shearing such as a jet nozzle. Thus, there isreally no fixed upper limit on the amount of polymer which can be used.

The crosslinking composition which is used in the practice of theinvention comprises:

(a) water;

(b) a first ingredient containing aluminum cations having a valence of3⁺ and comprising aluminum acetate;

(c) a second ingredient containing zirconium cations having a valence of4⁺ and selected from the group consisting of:

(i) zirconium lactate;

(ii) a zirconium admixture comprising:

(A) a zirconium compound selected from the group consisting of zirconiumoxychloride, zirconium acetate, zirconium tetrachloride, zirconiumorthosulfate, zirconium carbonate, zirconium ammonium carbonate, andmixtures thereof;

(B) an alpha-hydroxy acid represented by the following formula: ##STR5##wherein: R is selected from the group consisting of hydrogen and analkyl group having 1 to about 3 carbon atoms;

(C) an amine compound represented by the formula: ##STR6## wherein: R₁is a hydroxyalkyl group having 1 to about 3 carbon atoms;

R₂ is selected from the group consisting of an alkyl group having 1 toabout 3 carbon atoms and a hydroxyalkyl group having 1 to about 3 carbonatoms;

R₃ is selected from the group consisting of hydrogen, an alkyl grouphaving 1 to about 3 carbon atoms and a hydroxyalkyl group having 1 toabout 3 carbon atoms; and,

(iii) mixtures of (i) and (ii).

The zirconium cations and aluminum cations should be present in thecrosslinking composition in an amount sufficient to produce a weightratio of zirconium cations to aluminum cations of from about 1 to 1 toabout 10 to 1, and more preferably from about 2 to 1 to about 4 to 1.Most preferably the weight ratio of zirconium cations to aluminumcations is about 2.

The preferred crosslinking composition contains zirconium lactate, whichis available from Zirtech, Inc. of Gainesville, Florida, and aluminumacetate which is available from Niacet and the zirconium cations havinga valence of 4⁺ and the aluminum cations having a valence of 3⁺ arepresent in the crosslinking composition in an amount sufficient toproduce a weight ratio of zirconium cations to aluminum cations of about2.

When the zirconium admixture is utilized in the crosslinkingcomposition, methods of its preparation are disclosed in copending U.S.patent application 525,597 which is assigned to the assignee of thepresent invention and is hereby incorporated by reference.

Examples of suitable alpha-hydroxy acids which can be utilized in thezirconium admixture include lactic acid and glycolic acid. The preferredalpha-hydroxy acid is lactic acid.

Examples of suitable amine compounds which can be utilized in thezirconium admixture include diethanolamine, triethanolamine, anddimethylethanolamine. The preferred amine is triethanolamine.

The quantity of zirconium compound having a valence of 4⁺, acid, andamine used in the zirconium admixture will vary over a wide range.Generally, about 1 mole of zirconium cations having a valence of 4⁺ isused with about 2 to about 5 moles of the alpha-hydroxy acid and about 1to 5 moles of the amine.

A particularly preferred zirconium admixture comprises zirconiumoxychloride in an amount sufficient to produce one mole of zirconiumcations having a valence of 4⁺, about 2 moles of lactic acid, and about2 moles of triethanolamine.

The zirconium cations used in the crosslinking composition have a 4⁺valence and the aluminum cations have a valence of 3⁺. Although thecrosslinking mechanism is not totally understood, it is believed thatthe valence of the zirconium and aluminum cations does not change duringthe crosslinking of the composition with the polymers.

The amount of crosslinking composition used to carry out the method ofthe invention will vary over a wide range and therefore the amounts willvary according to the formation to be treated. Preferably, however, goodresults have been achieved when the combined weight of zirconium cationshaving a valence of 4⁺ and the aluminum cations having a valence of 3⁺are present in the crosslinking composition in amounts of from about 1.0to about 75.0, more preferably, from about 2.0 to about 50.0 percent byweight of the polymer and most preferably from about 3.0 to about 5.0percent by weight of the polymer.

The crosslinking composition is prepared preferably by adding to waterthe first and second ingredients of the crosslinking composition andadjusting the pH of the mixture from about 3 to about 11, and preferablyfrom about 6 to about 8.

Preferably, the crosslinking composition is used in the method of thepresent invention at a pH of from about 3 to about 11 and moreprefereably at a pH of from about 6 to about 8.

The term "water" is used generally herein and in the Claims, unlessotherwise specified, to include brines and fresh water.

The crosslinking composition and aqueous mixtures containing the waterdispersible hydrophilic organic polymer can be prepared from eitherfresh water or brine water having high concentrations of multivalentions such as Ca⁺⁺, Ba⁺⁺, Mg⁺⁺, CO₃ ⁼, and SO₄ ⁼. By high concentrations,it is meant at least 300 to about 10,000 ppm by weight of multivalentions based on the weight of the brine water. This feature isparticularly desirable when the performance of the method of theinvention is carried out at a location where fresh water is notparticularly accessible

On some occasions, the surfaces of the formation to be treated arecovered with materials such as hydrocarbons. If this covering is removedfrom the surface prior to the treatment, a treatment wherein thepermeability of the formation is reduced is better achieved. Therefore,sometimes an agent is utilized which removes the hydrocarbons from thesurfaces of the formation prior to the treatment. Agents which can beused include oxidizing agents such as hydrogen peroxide, potassiumpermanganate, nitric acid, and the like. These agents are well known inthe art and the selection of the agent will depend on the formation tobe treated.

In one embodiment of the present invention, the mixture comprising waterand the water dispersible hydrophilic organic polymers having amolecular weight greater than 100,000 and containing carboxylfunctionality are mixed with the crosslinking composition and theresulting mixture is injected through a well into the subterraneanformation. The mixture is directed to that portion of the subterraneanformation where it is desired that the permeability be altered. Afterthe injection of the above-described mixture, a spacer fluid ispreferably injected into the well to displace the mixture from thetubing and out into the formation. Preferably the volume of the spacerfluid is the volume needed to displace all the treating fluids out inthe formation plus five barrels per vertical foot of interval to betreated. The well is then preferably shut-in for a period of time,preferably about 48 hours.

In another embodiment of the present invention, a first mixturecomprising water and a water dispersible hydrophilic organic polymerhaving a molecular weight greater than 100,000 and containing carboxylfunctionality is injected through a well into the subterranean formationwhereby the polymer contacts that portion of the formation where thechange in permeability is desired. Optionally, a spacer fluid such as abrine solution is next injected into the well and thus contacts theformation. After the spacer fluid injection is completed, thecrosslinking compound is injected into the well bore and into theformation whereby the crosslinking composition contacts the polymer inthe formation. Optionally, a spacer fluid such as brine can be injectedinto the well and into contact with the formation. Finally, a secondmixture comprising water and a water dispersible hydrophilic organicpolymer having a molecular weight greater than 100,000 and containingcarboxyl functionality is injected into the well and into the formation.The steps of injecting the crosslinking composition and the secondorganic polymer can be repeated if necessary. The well is thenpreferably shut-in for a period of time, preferably about 48 hours. Thisembodiment is used primarily for treating waterflood injection wells.

Spacer fluids that can be used in the present invention are well knownin the art and include brine solutions, alkali metal halide solutionsand the like.

The amount of total polymer used to carry out the method of the presentinvention will vary over a wide range depending upon the formation to betreated.

The invention is further exemplified by the examples below and they arepresented to illustrate certain specific embodiments of the invention,but are not to be intended to be construed so as to be restrictive ofthe scope and spirit thereof.

EXAMPLE I

A series of aqueous gels were prepared using the crosslinkingcomposition of the present invention and 7 percent hydrolyzedpolyacrylamide.

The gels were prepared by adding 100 grams of either fresh or brinewater containing 7 percent hydrolyzed polyacrylamide to a beaker. Theaqueous crosslinking composition was prepared using 100 grams of eitherfresh or brine water. The polyacrylamide solution and crosslinkingcomposition were added together with stirring and viscosity readingswere taken at selected time intervals of the resulting composition usinga Brookfield Model LVT viscometer, No. 1 spindle, 6 r.p.m. at ambienttemperature.

The brine water used in the tests had the following compositions:

    ______________________________________                                        BRINE 1                                                                       Salt           % by Weight                                                    ______________________________________                                        Na.sub.2 SO.sub.4                                                                            0.4                                                            NaHCO.sub.3    0.1                                                            NaCl           5.6                                                            MgCl.sub.2.6H.sub.2 O                                                                        3.3                                                            CaCl.sub.2.2H.sub.2 O                                                                        1.1                                                            ______________________________________                                    

    ______________________________________                                        BRINE 2                                                                       Salt           % by Weight                                                    ______________________________________                                        Na.sub.2 SO.sub.4                                                                            0.002                                                          NaHCO.sub.3    0.03                                                           NaCl           1.36                                                           MgCl.sub.2.6H.sub.2 O                                                                        0.141                                                          CaCl.sub.2.2H.sub.2 O                                                                        0.382                                                          ______________________________________                                    

The aqueous crosslinking compositions used in the tests had thefollowing ingredients:

    ______________________________________                                        Crosslinking                                                                  Composition                                                                             Composition      Active Metal                                       Designation                                                                             (moles)          (% by weight)                                      ______________________________________                                        A         Al(OH).sub.2 (CH.sub.3 CO.sub.2).1/3HBO.sub.3                                                  4.6                                                B         Zirconium Oxychloride (1)                                                                      6.4                                                          Lactic Acid (2)                                                               Triethanol Amine (2)                                                C         Zirconium Lactate                                                                              5.18                                               ______________________________________                                    

The results of these tests are shown in Table I.

                  TABLE I                                                         ______________________________________                                                                   pH                                                      Crosslinking                                                                             Weight Ratio                                                                             Poly-                                                   Composition                                                                              Crosslinking                                                                             mer             Viscos-                            est  (Volume    Composition                                                                              Solu-                                                                              Water Time ity                                No.  Ratio)     to Polymer tion Used  (hr.)                                                                              (cps)                              ______________________________________                                         1   B          3,000/2,500                                                                              7.4  Fresh 15   310                                 2   A + B (1:2)                                                                              1,500/2,500                                                                              7.4  Fresh 15   20,000                              3   A          500/2,500  7.4  Fresh 15   220                                 4   B          1,500/2,500                                                                              7.4  Fresh 15   105                                 5   A          250/2,500  7.4  Fresh 15   120                                 6   A + B (1:2)                                                                              750/2,500  7.4  Fresh 15   150                                 7   A          1,000/2,500                                                                              7.2  Brine 1                                                                              3   9,200                               8   A          500/2,500  7.2  Brine 1                                                                              3   13,000                              9   A          250/2,500  7.2  Brine 1                                                                             18   45                                 10   A          125/2,500  7.2  Brine 1                                                                             18   32                                 11   C          3,000/2,500                                                                              7.2  Brine 1                                                                              3   8,500                              12   C          1,500/2,500                                                                              7.2  Brine 1                                                                              3   8,000                              13   C          750/2,500  7.2  Brine 1                                                                             15   700                                14   A + C (1:1)                                                                              500/2,500  7.2  Brine 1                                                                              3   19,500                             15   A + C (1:2)                                                                              500/2,500  7.2  Brine 1                                                                             18   20,000                             16   A + C (1:3)                                                                              500/2,500  7.2  Brine 1                                                                             18   3,350                              17   A + C (1:6)                                                                              500/2,500  7.2  Brine 1                                                                             18   720                                18   A + C (1:1)                                                                              500/2,500  9.0  Brine 1                                                                             17   560                                19   A + C (1:1)                                                                              500/2,500  7.0  Brine 1                                                                             17   20,000                             20   A + C (1:1)                                                                              500/2,500  5.0  Brine 1                                                                              2   15,900                             21   A + C (1:1)                                                                              500/2,500  3.0  Brine 1                                                                              2   11,000                             22   A + B (1:1)                                                                              500/2,500  7.2  Brine 1                                                                              4   9,900                              23   A + B (1:2)                                                                              500/2,500  7.2  Brine 1                                                                              4   1,800                              24   A + B (1:3)                                                                              500/2,500  7.2  Brine 1                                                                             18   320                                25   A + B (1:6)                                                                              500/2,500  7.2  Brine 1                                                                             18   260                                ______________________________________                                    

EXAMPLE II

A series of tests were performed in the same manner as Example I exceptthat the viscosity of the crosslinking composition was visuallyobserved. The results of these tests are shown in Table II.

                                      TABLE II                                    __________________________________________________________________________               Weight Ratio                                                          Crosslinking                                                                          Crosslinking                                                                         pH                                                          est                                                                              Composition                                                                           Composition                                                                          Polymer                                                                            Water                                                                             Time                                               No.                                                                              (Volume Ratio)                                                                        to Polymer                                                                           Solution                                                                           Used                                                                              (hr.)                                                                            Results                                         __________________________________________________________________________    1  A + B (1:2)                                                                           1,500/1,000                                                                          6.7  Brine 2                                                                           10 lipping gel                                     2  A + B (1:2)                                                                           750/1,000                                                                            6.7  Brine 2                                                                           10 lipping gel                                     3  A + B (1:2)                                                                           325/1,000                                                                            6.7  Brine 2                                                                           24 no lipping gel                                  4  B       750/1,000                                                                            6.9  Brine 2                                                                           24 no lipping gel                                  5  A       500/1,000                                                                            6.9  Brine 2                                                                           24 no lipping gel                                  __________________________________________________________________________

EXAMPLE III

Tests were conducted to determine the residual resistance factor (RRF)of two cores using the method of the present invention. The cores wereconnected in series with one another and contained Berea sandstone, andwere about 15/16" in diameter and about 4" in length.

The tests were carried out by the following steps:

a. Pump through the cores a brine solution until the differentialpressure across the cores is stable. The brine solution comprised Brine1.

b. Pump through the cores at a constant flow rate of 1 ml/min an aqueoussolution comprising 500 ppm of a copolymer of 93.0% by weight acrylamideand 7.0% by weight acrylic acid and 2% by weight of a crosslinkingcomposition. A volume of 100 ml of the aqueous solution was pumpedthrough the cores.

c. Pump a brine solution through the cores until the differentialpressure across the cores is stable.

The results of this test were measured in residual resistance factor(RRF). ##EQU1##

The permeabilities for the RRF were measured by the pumping pressurethrough the cores, before and after treatment.

The results of these tests are shown in Table III.

                  TABLE III                                                       ______________________________________                                               Crosslinking                                                           Test   Composition   RRF       RRF                                            No.    (Volume Ratio)                                                                              (1st Core)                                                                              (2nd Core)                                     ______________________________________                                        1      C             1.67      2.30                                           2      A             1.57      2.36                                           3      A + C (1:1)   4.4       2.1                                            ______________________________________                                    

The results of these tests show very efficient diversion using thecrosslinking compositions of the present invention.

Although certain preferred embodiments of the invention have been hereindescribed for illustrative purposes, it will be appreciated that variousmodifications and innovations of the procedures and compositions recitedmay be effected without departure from the basic principals whichunderlie the invention. Changes of this type are therefore deemed to liewithin the spirit and scope of the invention except as may benecessarily limited by the amended claims or reasonable equivalentsthereof.

What is claimed is:
 1. A method of altering the permeability of asubterranean formation comprising contacting said formation with anaqueous mixture comprising:I. a water dispersible hydrophilic organicpolymer having a molecular weight greater than 100,000 and containingcarboxyl functionality; and II. a crosslinking compositioncomprising:(a) water; (b) a first ingredient containing aluminum cationshaving a valence of 3⁺ and comprising aluminum acetate; (c) a secondingredient containing zirconium cations having a valence of 4⁺ andselected from the group consisting of:(i) zirconium lactate; (ii) azirconium admixture comprising: (A) a zirconium compound selected fromthe group consisting of zirconium oxychloride, zirconium acetate,zirconium tetrachloride, zirconium orthosulfate, zirconium carbonate,zirconium ammonium carbonate, and mixtures thereof; (B) an alpha-hydroxyacid represented by the following formula: ##STR7## wherein R isselected from the group consisting of hydrogen and an alkyl group having1 to about 3 carbon atoms; (C) an amine compound represented by theformula ##STR8## wherein: R₁ is a hydroxyalkyl group having 1 to about 3carbon atoms; R₂ is selected from the group consisting of an alkyl grouphaving 1 to about 3 carbon atoms and a hydroxyalkyl group having 1 toabout 3 carbon atoms; R₃ is selected from the group consisting ofhydrogen, an alkyl group having 1 to about 3 carbon atoms, and ahydroxyalkyl group having 1 to about 3 carbon atoms; and,(iii) mixturesof (i) and (ii); wherein said zirconium cations and said aluminumcations are present in said crosslinking composition in an amountsufficient to produce a weight ratio of zirconium cations to aluminumcations of from about 1 to 1 to about 10 to 1 and said crosslinkingcomposition has a pH of from about 3 to about
 11. 2. The method recitedin claim 1 wherein said water dispersible hydrophilic organic polymer isselected from the group consisting of carboxyalkyl guar wherein thealkyl group has 1 to about 3 carbon atoms, carboxyalkylhydroxyalkyl guarwherein the alkyl groups have 1 to about 3 carbon atoms, xanthan gum,polyacrylamide wherein about 5 to about 75 percent of the carboxamidegroups are hydrolyzed to carboxyl groups, polymethacrylamide whereinabout 5 to about 75 percent of the carboxamide groups are hydrolyzed tocarboxyl groups, cellulose ethers, a copolymer of about 5 to about 70percent by weight acrylic acid or methacrylic acid copolymerized withacrylamide or methacrylamide, and mixtures thereof.
 3. The methodrecited in claim 2 wherein said second ingredient is selected from thegroup consisting of zirconium lactate and an admixture comprising aboutone mole of zirconium oxychloride, about 2 moles of lactic acid, andabout 2 moles of triethanolamine.
 4. The method recited in claim 2wherein said pH of said crosslinking composition is from about 4 toabout
 11. 5. The method recited in claim 2 wherein the ratio ofzirconium cations to aluminum cations is about 0.5.
 6. The methodrecited in claim 5 wherein the zirconium cations and aluminum cations insaid crosslinking composition are present in the range of from about 3.0to about 5.0 percent by weight of the polymer.
 7. The method recited inclaim 6 wherein said polymer of said first and second mixtures ispresent in said aqueous mixture in the range of from about 0.0025 toabout 5.0 weight percent of water.
 8. The method recited in claim 7wherein said polymer is selected from the group consisting ofpolyacrylamide wherein 7 percent of the carboxamide groups arehydrolyzed to carboxyl groups, polyacrylamide wherein 30 percent of thecarboxamide groups are hydrolyzed to carboxyl groups and mixturesthereof.
 9. A method of altering the permeability of a subterraneanformation comprising:sequentially contacting the formation with:I. afirst aqueous mixture comprising a water dispersible hydrophilic organicpolymer having a molecular weight of at least 100,000 and containingcarboxyl functionality; II. a crosslinking agent having a pH of fromabout 4 to about 11 and comprising:(a) water; (b) a first ingredientcontaining aluminum cations having a valence of 3+ and comprisingaluminum acetate; (c) a second ingredient containing zirconium cationshaving a valence of 4+ and selected from the group consisting of:(i)zirconium lactate; (ii) a zirconium admixture comprising: (A) azirconium compound selected from the group consisting of zirconiumoxychloride, zirconium acetate, zirconium tetrachloride, zirconiumorthosulfate, zirconium carbonate, zirconium ammonium carbonate, andmixtures thereof; (B) an alpha-hydroxy acid represented by the followingformula: ##STR9## wherein: R is selected from the group consisting ofhydrogen and an alkyl group having 1 to about 3 carbon atoms; (C) anamine compound represented by the formula: ##STR10## wherein: R₁ is ahydroxyalkyl group having 1 to about 3 carbon atoms; R₂ is selected fromthe group consisting of an alkyl group having 1 to about 3 carbon atomsand a hydroxyalkyl group having 1 to about 3 carbon atoms; R₃ isselected from the group consisting of hydrogen, an alkyl group having 1to about 3 carbon atoms, and a hydroxyalkyl group having 1 to about 3carbon atoms; and,(iii) mixtures of (i) and (ii); wherein said zirconiumcations and said aluminum cations are present in said crosslinkingcomposition in an amount sufficient to produce a weight ratio ofzirconium cations to aluminum cations of from about 1 to 1 to about 10to 1 and said crosslinking composition has a pH of from about 3 to about11; and, III. a second aqueous mixture comprising a water dispersiblehydrophilic organic polymer having a molecular weight of at least100,000 and containing carboxyl functionality.
 10. The method recited inclaim 1 wherein said water dispersible hydrophilic organic polymer ofthe first and second mixture is selected from the group consisting ofcarboxyalkyl guar wherein the alkyl group has 1 to about 3 carbon atoms,carboxyalkylhydroxyalkyl guar wherein the alkyl groups have 1 to about 3carbon atoms, xanthan gum, polyacrylamide wherein about 5 to about 75percent of the carboxamide groups are hydrolyzed to carboxyl groups,polymethacrylamide wherein about 5 to about 75 percent of thecarboxamide groups are hydrolyzed to carboxyl groups, cellulose ethers,a copolymer of about 5 to about 70 percent by weight acrylic acid ormethacrylic acid copolymerized with acrylamide or methacrylamide, andmixtures thereof.
 11. The method recited in claim 10 wherein said secondingredient is selected from the group consisting of zirconium lactateand an admixture of about 1 mole of zirconium oxychloride, about 2 molesof lactic acid, and about 2 moles of triethanolamine.
 12. The methodrecited in claim 11 wherein the zirconium cations and aluminum cationsin said crosslinking composition are present in the range of from about3.0 to about 5.0 percent by weight of the polymer and the ratio ofzirconium cations to aluminum cations is about 0.5.